A natural backdrop: Regent’s Park Open Air Theatre

Haworth Tompkins’ timber interventions to Regent’s Park Open Air Theatre make sure the park is the star of the show, writes Felix Mara. Photography by Philip Vile

London’s reputation as a great city rests firmly on the abundance and quality of its green spaces, most notably Regent’s Park. By comparison, the world’s other great cities; Paris, New York and Tokyo seem deprived.

But Regent’s Park is not simply a lung or a place without buildings. It is the starting point for London’s greatest urban set-piece, the picturesque sequence of spaces, thoroughfares and buildings devised by John Nash which snakes, swivels and ploughs its way down to the former Prince Regent’s residence at Carlton House Terrace on the edge of St James’s Park.

In fact, Regent’s Park has many buildings, not only those that form its white stucco frame, but also those within. These harmonise or disappear altogether behind bushes and copses, playing an essential part as humble utilitarian servants or centres of activity that bring the park to life. The park’s aerial view is a revelation.

Regent’s Park’s Open Air Theatre is one of its best secrets. It started its seasonal life as a deck chair auditorium, open to the sky, then, in 1976, Howell, Killick Partridge & Amis added a steeply-raked auditorium which, with a capacity of 1,240, is one of London’s largest. In 1999, Haworth Tompkins reconfigured the layout and front and back of house areas, working closely with Camlin Lonsdale Landscape Architects to transform its setting into an environment that felt magical, lyrical and very seasonal.

In May, the theatre celebrated its 80th year by opening year-round office accommodation previously located off-site, improved dressing rooms, workshops and a new box office and sheltered seating canopy, all designed by Haworth Tompkins, specialists not only in theatrical architecture, but also in imaginative re-workings of existing buildings.

Haworth Tompkins stood by their original approach of using living and fabricated screens to conceal construction and integrate the theatre complex with its landscape setting. It was an accretive and unforced, though ultimately contrived, strategy that is a microcosm of the layout of the park itself. As a result, the theatre has retained its quirky ‘Pimms on the lawn’ quality while providing facilities for highly professional, accomplished and adventurous productions.

The new box office, which will be open all year round, addresses the park and serves as the theatre’s public face. Beyond this gateway, the radial site perimeter, which follows the fan-geometry of the auditorium, has been lined with a new canvas seating canopy that complements the existing bar accommodation and provides intimate booth spaces. Back-of-house facilities have been replaced by the large, linear, new backstage building, which is divided into two sections and houses offices, dressing rooms and wardrobe. It follows the geometry of Regent’s Park’s inner circle at the complex’s northern boundary, clad in rough-sawn larch boarding, which will in time harmonise with its sylvan setting. ‘We conceived this addition as an inhabited wall,’ says director Steve Tompkins.

The box office morphs from a low-key off-season structure with black-stained softwood cladding, posters, gilded highlights and sign to alternating summer configurations with its four-metre wide civil engineering-grade steel-framed doors closed or opened to reveal their inner lining of gilded foliage. Like the new backstage building, the box office is constructed in cross-laminated timber (CLT) fabricated off-site, enabling the additions to be completed during the six-month off-season shutdown, also minimising loadings and therefore foundations and interference with the roots of existing trees. The larch cladding to the backstage building is alternately stained and unstained, forming camouflaging vertical strips and finned rather than solid end walls, help it to read as a nonbuilding. Internally, the timber surfaces of this building are exposed and knotty. Haworth Tompkins eschewed bland symphonies in raw engineered timber by using it in dialogue with bold supergraphics, their numbers so big you can hardly read them, rich colours and spongy carpets of cork-rubber compound flooring.

The environmental design of the backstage building is simplicity itself, using workaday low-energy construction with a modest CO2 emissions profile. It also has natural ventilation, good daylight factors, low solar gain and discomfort glare, achieved by concentrating windows on its north facade and planting projecting fins at jamb corners, which help screen out noise and enliven the elevations. Things can go horribly wrong when architects fail to coordinate services with CLT construction. But not here. Haworth Tompkins ran services in a simple bespoke raised access floor at mezzanine level, and from this zone they dropped down to serve the spaces below. Along with highlights in contrasting materials and good coordination, there was another ingredient in Haworth Tompkins’ successful use of engineered timber: Liam Dewar, founding director of timber sub-contractor Eurban studied architecture under Tompkins at the University of Bath, so he had to do a good job.

Working detail

The woodland setting is reinforced by the recessive language of the new building, which has been designed to blur the distinction between building and landscape. The building is predominantly timber, constructed from prefabricated timber panels and clad in vertical larch boards.

The main structure was erected in less than three weeks and requires relatively small piled foundations. The thin concrete slab, with a void-former beneath, allowed the building to be built close to the neighbouring trees.

The finish to the timber surface is critical to the overall feel of the facade; with the natural richness of rough-sawn boards preferred to the more industrial look of smooth, planed boards. The dark stained larch cladding is cut back at window openings to reveal bands of untreated timber sandwiched between deep projecting fins, with a natural finish on the inside face and dark stain on the other.

Echoing the form of the trees, the fins animate the facade, but also serve practical functions; screening the rooms behind and allowing windows to open while maintaining security.

A breather membrane and rigid insulation are located behind the cladding and the joints of the cross-laminated panels are taped on the outer face for airtightness. The internal surface of the timber panels is exposed and sealed with a clear matt fire-retardant sealant.

A slim aluminium angle is affixed to the top of the timber boards at roof level to prevent water ingress into the end grain. The roof behind is finished with a single ply membrane, terminated in a folded grey metal coping.

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